A particular type of gas turbine engine that may be used to power aircraft is a turbofan gas turbine engine. A turbofan gas turbine engine may include, for example, five major sections, a fan section, a compressor section, a combustor section, a turbine section, and an exhaust section. The fan section is positioned at the front, or “inlet” section of the engine, and includes a fan that induces air from the surrounding environment into the engine, and accelerates a fraction of this air toward the compressor section. The remaining fraction of air induced into the fan section is accelerated into and through a bypass plenum, and out the exhaust section.
The compressor section raises the pressure of the air it receives from the fan section to a relatively high level. In a multi-spool engine, the compressor section may include two or more compressors. For example, in a triple spool engine, the compressor section may include a high pressure compressor, and an intermediate compressor. The compressed air from the compressor section then enters the combustor section, where a ring of fuel nozzles injects a steady stream of fuel. The injected fuel is ignited by a burner, which significantly increases the energy of the compressed air.
The high-energy compressed air from the combustor section then flows into and through the turbine section, causing rotationally mounted turbine blades to rotate and generate energy. Specifically, high-energy compressed air impinges on turbine vanes and turbine blades, causing the turbine to rotate. The air exiting the turbine section is exhausted from the engine via the exhaust section, and the energy remaining in this exhaust air aids the thrust generated by the air flowing through the bypass plenum.
Many gas turbine engines, such as the above-described turbofan gas turbine engine, include one or more bleed valve assemblies. The bleed valve assemblies are used to selectively bleed some of the compressed air from the compressor section, and most notably the high pressure compressor, before it passes through the remaining sections of the engine. As is generally known, selectively bleeding air from a compressor, via the bleed valve assemblies, is conducted to preclude the compressor from exceeding its surge limits. For turbofan gas turbine engines, such as the one described above, the bleed air may be discharged into the bypass plenum.
Typically, a bleed valve assembly includes a bleed valve and a bleed air duct. When the bleed valve is open, the bleed valve duct directs bleed air flow into the bypass plenum. In most instances, the outlet ports of these discharge ducts may include a flow diffuser and/or noise attenuator through which the bleed air is discharged. Although present bleed valve assemblies and flow diffuser/noise attenuator designs are generally safe, robust, and reliable, these devices do suffer certain drawbacks. For example, the bypass air in the bypass plenum is typically at a relatively low temperature. As such, components within the plenum, including the plenum itself, may not be designed to withstand relatively high temperature air. However, the bleed air from the compressor section is typically at a relatively high temperature. Thus, when the bleed air is discharged into the bypass plenum, if it is not sufficiently mixed with the relatively low temperature bypass air, the temperature of various components within the bypass plenum, and/or the plenum itself, can reach undesirably high temperatures. In addition, the configuration of some previously designed deflectors can result in relatively high stresses in various regions thereof.
Hence, there is a need for a bleed valve assembly and flow deflector that improves the mixing of relatively high temperature bleed air with relatively low temperature bypass air, to thereby minimize the increase in temperature of various components within the bypass plenum, and that is structurally enhanced to reduce stresses in the deflector. The present invention addresses one or more of these needs.